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old sub freak

mpg/ rpm, what works best??

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i installed a"mileometer" [vacume gage} on my ea81 hacth. its sposed to tell you when you get the best milage per vacume presure. well on the freeway at say 65mph in 3rd gear, 3500 rpms the guage reads GOOD/ high vacume. i shift to 4th,2000-2500rpms it reads POOR low vacume. i have 14 in tires so i'm some what guessing on the mph. i'm to lazy to really check the mpg{hey thats why i bought the mileometer} so i would think you would get better gas milage in 3rd/3500rpm. what are your thougts? and i'll sure try to do hood river. toddw/northern aliance crew

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I haven't done any scientific tests to prove this, but my soob sure seems a lot happier running between 3000 and 3500 than between 2000 and 2500. Below about 2800 rpm, it starts to fall off the torque curve and has to struggle, which is bad for fuel economy.

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you have just discovered the reason we run the 81/82 4 speed D/R with big tires - or 4th gear of a 5 speed D/R. The gearing on the 81/82 is such that 4th is actually usable with my 28's.....

 

GD

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with my RX and the 16inch big wheels I seemed to get the best fuel econ between 3000 and 3500 rpm on the highway. Since then I have put the stock wheels back on for handling in the snow, even with stock tires it pulls better all around but seems to want to ride between 3200 and 3700 rpm. I seem to be getting about 26-29 mpg on the highway and somewhere around 21-24 in the city.

 

So for best fuel economy I keep it between 3 and 4 thousand rpm, and that is right where the torque is, when you put the gas down it wants to pull rather than bog.

 

This is of course with a carbbed block, turbo top end, 87 octane fuel, stock wheels, and stock full-time-4x4 d/r.

 

I often wonder if lo-range would be better for fuel economy, because there would be less load on the engine, but it would be turning higher rpm to maintain the same speed, it is be more practical to use in the city where you don't get up to high speeds.

 

However I have hit the highway in adverse conditions and maintained about 4500 rpm (75 mph) in lo range for extended periods of time and have had no trouble.

 

You should get a little better economy than me if you have a part time 4x4 tranny, less gears to turn, less load, etc.

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well my ea81 hatch, all stock on the long trips i run at about 3500 rpms which is about 73 mph... gets 32mpg

 

short trips to work it runs about 2000-2500 at 55-65.. gets about 26 mpg this way..

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